The private pilot reported that his single-engine experimental airplane experienced a complete loss of engine power on initial climb after takeoff. An attempt to re-start the engine was successful and the pilot elected to return to the airport and land. Shortly after the restart, the engine again experienced a complete loss of power and attempts to restart were unsuccessful. The pilot selected a forced landing to an area of small trees rather than an alternative forced landing in a lake. During the landing the airplane sustained substantial damage and came to rest upright in a nose down attitude. The pilot and his passenger received minor injuries. In a written statement from the passenger the airplane was fueled prior to take off from several hand carried gas cans that were brought to the airport by the pilot. Although the owner/builder of the airplane reported that the airplane regularly used auto gas and that water in the fuel was common, the cause of the loss of the engine power could not be determined.